[arm-allstar] Open board cm108 sound fobs

[Doug Crompton]

Alan,

  As Dave said the "B" model cm108 and cm119 have lower audio levels. In
most cases this can be compensated for with rxboost and/or setting the
levels up. In many cases there is also a resistor pad in the mod in series
that can be lowered in value or eliminated. Did you mod the FOB yourself or
buy it mod'ed?

The "B" models work fine with most radios but some need more drive. Some
need more drive then even the non "B" models will supply. In that case your
only choice is to either build an op-amp amplifier or use one of the
commercial units that already has one built in like the DMK-URI or the
RA-35 which actually uses power op-amps so you can really blast a hard to
drive radio.

If you are a builder then adding an op-amp is not a big deal. A single
supply rail-to-rail op-amp and the available 5 volts on the board would
work fine. Also check the pinout for the radio you are using as for example
the 6 pin din radio has both (what they call) 9600 and 1200 baud pins .
They have different levels associated with them. Perhaps you are using the
wrong one? Keep in mind that the 9600 baud one would require emphasis
and/or deemphasis in Allstar while 1200 would not.


*73 Doug*

*WA3DSP*

*http://www.crompton.com/hamradio <http://www.crompton.com/hamradio>*



On Thu, Aug 3, 2017 at 4:44 AM, "Alan Matthews via arm-allstar" <
arm-allstar at hamvoip.org> wrote:

> Guys
>
> I have been using the open board style cm108 sound fobs from china to
> build my nodes. I have noticed recently that the tx audio into the system
> (what you hear on your end) is very low.
>
> When running the simple usb tune option 2 i cannot get the audio level  to
> get anywhere near the markers.
>
> when using the baofeng bf888s its not to bad, however connected to my
> ft991 or 7800 the levels are extremely low. I never had this problem with
> startech fobs.
>
> My URI fob works great with the 991.
>
> Have any of you guys experienced this issue.
>
> thanks in advance.
>
> regards Alan
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